Iron-nickel alloy material for shadow mask with excellent suitability for etching

ABSTRACT

The inv ntion is a Fe—Ni alloy mat rial comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.0001-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt % and the reminder being Fe and inevitable impurities, and containing not more than 0.02 wt % of one or more MnO—SiO 2 —Al 2 O 3  inclusion, SiO 2  inclusion and MgO—Al 2 O 3  inclusion insoluble in an aqueous solution of ferric chloride, and is to provide electronic materials for shadow mask and the like having a good hole shape in an etching treatment and a high quality.

TECHNICAL FIELD

[0001] This invention relates to a Fe—Ni alloy material for shadow masks having an excellent etching workability, and particularly provides a Fe—Ni alloy material containing a non-metallic inclusion(s) insoluble in an aqueous solution of ferric chloride.

BACKGROUND ART

[0002] Heretofore, the Fe—Ni alloy materials have been used as various functional materials including a magnetic material, a lead frame and a shadow mask. These materials are worked to a product thickness of about 0.1-1 mm in accordance with applications. Particularly, Fe-36 wt % Ni alloy is low in the thermal expansion coefficient and is useful as a shadow mask material. This shadow mask material is usually produced subjecting a Fe—Ni alloy sheet to an etching treatment using an aqueous solution of ferric chloride.

[0003] As to the etching workability of the shadow mask material, there are many inventions in view of surface properties (JP-A-4-99152 and so on), plane orientation (JP-A-1-247558 and so on) and the like. Also, study examples focusing attention to non-metallic inclusions contained in the alloy are disclosed in JP-A-61-84356 and JP-A-7-268558, but all of them aim only at the reduction of the non-metallic inclusion amount. However, even if the non-metallic inclusion amount is reduced, there may be a case that the deterioration of hole shape accompanied with the poor etching work is caused depending upon the kind and composition of th non-metallic inclusions.

[0004] That is, when hol s ar formed by th etching treatment using the aqueous solution of f rric chlorid at th production step of the shadow mask, if non-m tallic inclusions are existent in positions to b pierced and th etching is carried out, the shape of the holes in the shadow mask material is poor. Especially, if the non-metallic inclusions are soluble in the etching solution, the hole shape is further poor. Particularly, if the non-metallic inclusion is mainly composed of MgO or CaO, as shown in FIG. 1, the non-metallic inclusions existing on the surface of the thin sheet are dissolved in the etching solution and corrode Fe—Ni alloy therearound to cause a problem that the shape of the etched hole is deteriorated.

[0005] It is, therefore, an object of the invention to develop a technique capable of solving the above problems of the conventional technique and to provide a Fe—Ni alloy material for shadow mask having an excellent etching workability.

DISCLOSURE OF THE INVENTION

[0006] The inventors have made various studies with respect to the formation of non-metallic inclusion not causing the poor shape of the etched hole for solving the above problems. That is, Fe-36 wt % Ni alloy is first melted in a laboratory, and then CaO—SiO₂—Al₂O₃—MgO—F based slag is added to the alloy melt, and thereafter deoxidized with a deoxidizing agent such as Si, Mn, Al, Mg, Ca or the like to prepare a steel ingot. This steel ingot is forged or hot rolled and then cold rolled to a product thickness of 0.11 mm. Thereafter, it is etched with an aqueous solution of ferric chloride (45 Baume, temperature 60° C.), and corrosion state through inclusions around the etched hole portions is examined.

[0007] As a result, the inventors have found that when the non-metallic inclusion in the Fe—Ni alloy material has a composition of at least one or more of MnO—SiO₂—Al₂O₃, SiO₂ and MgO—Al₂O₃ spinel, the poor shape of th etched hol can be prevented and henc the Fe—Ni alloy having an excellent tching workability can be obtained.

[0008] Further, it has been confirmed that when a sum of CaO and MgO in the MnO—SiO₂—Al₂O₃ based inclusion exceeds 30 wt %, these oxides are dissolved in the etching solution to proceed corrosion and to cause poor hole shape.

[0009] The invention is based on the above knowledge. That is, the invention is a Fe—Ni-alloy material having an alloy composition characterized by comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.0001-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt %, Nb: 0.01-1.0 wt % and Co: 1-8 wt % and the reminder being Fe and inevitable impurities, and containing not less than 0.02 wt % of non-metallic inclusion insoluble in ferric chloride, i.e. MnO—SiO₂—Al₂O₃ based inclusion having a composition of MnO: 25-50 wt %, SiO₂: 40-60 wt % and Al₂O₃: 5-30 wt % and/or SiO₂ inclusion, or further such inclusion and MgO—Al₂O₃ spinel inclusion having a composition of Mgo: 5-45 wt % and Al₂O₃: 55-95 wt %. However, a sum of CaO and MgO as an oxide component included in the MnO—SiO₂—Al₂O₃ based inclusion is not more than 30 wt %.

BRIEF DESCRIPTION OF THE DRAWING

[0010]FIG. 1 is a microphotograph illustrating a shape of an etched hole resulted from inclusions.

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] The reasons the chemical components and composition of the alloy material according to the invention are limited to the above are described together with the action of Fe—Ni alloy.

[0012] Ni: 26-37 wt %

[0013] Since Ni is an element exerting upon the thermal expansion, it is known that the thermal expansion co fficient at 200° C. becom s minimum around 36 wt % in case of containing no Co. Also, in cas of containing Co, when a sum of Co and Ni contents is a rang of 35-38 wt %, the thermal expansion coefficient becomes small. Th refore, the Ni content is d fin d to be 26-37 wt %.

[0014] Si: 0.001-0.2 wt %

[0015] Si is an element required for not only the deoxidation of molten steel but also the control of inclusion composition to MnO—SiO₂—Al₂O₃ system or SiO₂. When the Si amount is less than 0.001 wt %, the inclusion composition can not be controlled to MnO—SiO₂—Al₂O₃ system or SiO₂ and it is difficult to ensure the necessary etching workability. While, when it exceeds 0.2 wt %, the thermal expansion coefficient becomes large and the required characteristics are not satisfied. In the invention, therefore, the Si amount is limited to 0.001-0.2 wt %. A preferable range is 0.01-0.1 wt %.

[0016] Mn: 0.01-0.6 wt %

[0017] Mn is an element useful for controlling the inclusion composition to MnO—SiO₂—Al₂O₃ system. However, it is an element raising the thermal expansion coefficient. From this viewpoint, it is desirable to be a lower concentration as far as possible. That is, when the Mn amount is less than 0.01 wt %, the inclusion composition can not be controlled to MnO—SiO₂—Al₂O₃ system, while when it exceeds 0.6 wt %, the thermal expansion coefficient is too large and the required characteristics are not satisfied. Therefore, the Mn amount is limited to 0.01-0.6 wt %. A preferable range is 0.03-0.4 wt %.

[0018] Al: 0.0001-0.003 wt %

[0019] Al is an element effective for controlling the inclusion composition to MnO—SiO₂—Al₂O₃ system or MgO—Al₂O₃ system having an excellent corrosion resistance. However, as the concentration of Al becomes high, the inclusion composition renders into alumina, which is apt to easily form cluster, and the surface properties are deteriorated and the required quality is not satisfied. In the invention, th refore, the Al amount is limited to 0.0001-0.003 wt %. A pr ferable rang is 0.0002-0.002 wt %.

[0020] Mg: not more than 0.001 wt %

[0021] Mg is a useful element from a viewpoint that the inclusion composition is controlled to MgO—Al₂O₃, but when it exceeds 0.001 wt %, the main body of the inclusion is MgO alone and badly affects the etching workability. Even if Mg is not contained, the inclusion composition is rendered into MnO—SiO₂—Al₂O₃ system having an excellent etching workability, so that the Mn amount is limited to not more than 0.001 wt %. It is preferably not more than 0.0009 wt %.

[0022] Ca: not more than 0.001 wt %

[0023] Ca is such an element that when it exceeds 0.001 wt %, the concentration of CaO in the inclusion rises and badly affects the etching workability. Therefore, it is desirable to reduce the addition of Ca as far as possible. From this point, Ca is limited to not more than 0.001 wt %. Preferably, it is not more than 0.0009 wt %.

[0024] Nb: 0.01-1.0 wt %

[0025] Nb has an effect of lowering the thermal expansion coefficient at a slight amount and is an effective element. However, when it exceeds 1.0 wt %, the thermal expansion coefficient inversely increases. Therefore, when Nb is added, it is 0.01-1.0 wt %. Preferably, it is a range of 0.02-0.5 wt %.

[0026] Co: 1-8 wt %

[0027] Co is an element exerting on the thermal expansion coefficient. In case of Fe—Ni alloy containing Co, when the Co amount is outside a range of 1-8 wt %, the thermal expansion coefficient becomes large, which is not suitable for shadow mask. Therefore, the Co amount is limited to 1-8 wt %.

[0028] In order to obtain the expected effects in the Fe—Ni alloy material according to the invention, it is concluded that it is necessary to control the composition of the non-metallic inclusion in form of oxides includ d in such F —Ni alloy matrix.

[0029] As th form of th non-metallic inclusion r quir d in the invention, th main component has a form of one or more of MnO—SiO₂—Al₂O₃ system, SiO₂, and MgO—Al₂O₃.

[0030] Particularly, it has been found that the composition of the MnO—SiO₂—Al₂O₃ based inclusion is good within ranges of MnO: 25-50 wt %, SiO₂: 40-60 wt % and Al₂O₃: 5-30 wt %. Because, when the composition is in the above range, the inclusion is vitrified and hardly causes the dissolution in the etching solution. However, when MnO exceeds 50 wt %, the phenomenon of dissolving in the etching solution is confirmed though it is not a level of CaO, MgO.

[0031] Similarly, the other two of MgO—Al₂O₃ and SiO₂ are insoluble in the aqueous solution of ferric chloride, so that they do not cause the poor hole shape.

[0032] From various experiments made by the inventors, it has been confirmed that when CaO or MgO is incorporated into the MnO—SiO₂—Al₂O₃ based inclusion, the corrosion considerably proceeds in the etching solution. Particularly, it is observed that when more than 30 wt % in total of CaO and MgO are incorporated into the MnO—SiO₂—Al₂O₃ based inclusion, the corrosion is conspicuous and the shape of the etched hole tends to be disordered. In the invention, therefore, the sum of CaO and MgO is 30 wt % as an upper limit. Preferably, it is suppressed to about 5 wt %, or further it is preferable not to contain them.

EXAMPLE

[0033] In an electric furnace is melted Fe—Ni alloy and the resulting molten alloy is subjected to a deoxidation treatment by adding CaO—SiO₂—Al₂O₃—MgO—F based slag in AOD or VOD. The molten alloy after the treatment is cast through a continuous casting machine to prepare a slab. Thereafter, the slab is hot rolled and then cold rolled to a product thickness of 0.11 mm. A test piece of 200 mm×400 mm is cut out from the thus obtained cold roll d sheet and pi rc d by etching in an aqueous solution of f rric chlorid (45 Baum, t mp rature 60° C.) to examine corrosion stat around the hole through inclusion, i.e. poor hol shape.

[0034] The evaluation method is as follows.

[0035] {circle over (1)} Chemical components: The test piece cut out from the slab is analyzed by a fluorescent X-ray analyzing apparatus.

[0036] {circle over (2)} Inclusion composition: A quantitative analysis on inclusions is randomly carried out on 20 points by using EDS (energy dispersion type analyzing apparatus).

[0037] {circle over (3)} Poor hole shape: 100 etched holes are randomly observed by an electron microscope to count the number of poor hole shapes.

[0038] In Table 1 are shown the contents of the examples and evaluation results thereof. In the invention examples, all of the inclusion compositions have concentrations of MnO, SiO₂ and Al₂O₃ within proper ranges and are controlled to a silicate having a sum of MgO and CaO of not more than 30 wt % or silica or spinel, and the poor hole shape due to the etching is not caused.

[0039] On the other hand, comparative examples are described below. In No. 10. the concentrations of Mg and Ca a re high and the sum of MgO and CaO in the silicate based inclusion exceeds 30 wt % and hence the poor hole shape is confirmed. In No. 11, the Si amount is outside the lower limit and the inclusion is a silicate mainly composed of MnO and hence the poor hole shape is confirmed. In No. 12, Mg is high and the inclusion is MgO only and hence the poor hole shape is caused. In No. 13, Ca is high and the inclusion is a silicate mainly composed of CaO and hence the poor hole shape is caused. In No. 14, the amount of Si largely exceeds the upper limit and there is no problem in the inclusion composition, but the th rmal expansion coefficient exceeds the required level to r nd r into a r j ct product. In No. 15, Al and Mg are high and the inclusion is spin 1 system, magn sia and alumina. As a r sult, not only the poor hole shap but also the poor surface quality due to alumina clust r ar simultaneously confirmed. In No. 16, th amount of Mn is outside the lower limit and the silicate based inclusion is outside the proper range and the sum of MgO and CaO exceeds 30%, and hence the poor hole shape is caused. TABLE 1 Evaluation of etching Analysis on 20 points by EDS Poor hole Inclusion composition (wt%) Niobium shape Chemical components (wt %) Silicate base Silica Spinel base oxide Magnesia Alumina (holes/ Ni Si Mn Al Mg Ca Nb Co n MnO Si0₂ Al₂O₃ MgO CaO n SiO₂ n MgO Al₂O₃ n Nb₂O₅ n MgO n Al₂O₃ 100 holes) Inven- 1 31.98 0.022 0.31 0.0003 0.0001 0.0004 — 5.03 18 31.4 44.3 12.4 4.1 7.8 0 2 6.5 93.5 0 0 0   0 tion 2 36.00 0.015 0.25 0.0005 0.0004 0.0005 — — 12 25.2 40.2 24.1 9.2 1.3 0 8 25.4 74.6 0 0 0   0 Exam- 3 35.98 0.121 0.42 0.0015 0.0005 0.0002 — — 10 27.1 41.2 28.1 3.2 0.4 2 100 8 36.1 63.9 0 0 0   0 ple 4 36.03 0.033 0.27 0.0002 0.0001 0.0002 0.16 — 20 48.1 45.2 5.5 0.3 0.9 0 0 0 0 0   0 5 35.06 0.162 0.52 0.0023 0.0009 0.0007 — — 0 0 20 43.2 56.8 0 0 0   0 6 36.01 0.042 0.03 0.0018 0.0002 0.0004 0.18 — 0 6 100 12 41.9 58.1 2 100 0 0   0 7 35.99 0.039 0.02 0.0020 0.0002 0.0005 0.16 — 0 8 100 12 29.1 70.90 0 0 0   0 8 36.00 0.003 0.02 0.0003 0.0003 0.0004 — — 8 25.3 40.2 9.5 15.2 9.8 12 100 0 0 0 0   0 9 36.04 0.026 0.29 0.0001 0.0001 0.0001 — — 17 26.2 58.1 10.5 2.3 2.9 0 3 36.3 63.7 0 0 0   0 Com- 10 36.01 0.022 0.36 0.0005 0.0012 0.0015 — — 20 23.4 20.5 10.2 23.8 22.1 0 0 0 0 0   5 para- 11 36.02 0.0005 0.45 0.0001 0.0001 0.0001 — — 20 80.6 16.5 0.2 2.1 0.6 0 0 0 0 0   2 tive 12 35.98 0.033 0.32 0.0012 0.0023 0.0005 — — 0 0 0 0 20 100 0  15 Exam- 13 36.02 0.011 0.35 0.0005 0.0005 0.0035 0.18 — 20 0.5 45.2 1.5 2.5 50.3 0 0 0 0 0  13 ple 14 36.05 0.356 0.38 0.0012 0.0004 0.0007 — — 15 25.5 41.2 28.1 3.2 2 0 5 42.1 57.9 0 0 0  *0 15 36.04 0.022 0.32 0.0045 0.0012 0.0004 — — 0 0 2 25.2 74.8 0 4 100 14 100  **4 16 36.00 0.021 0.005 0.0012 0.0008 0.0008 — — 18 0.2 43.4 10.2 23.5 22.7 0 2 23.4 76.6 0 0 0   5

INDUSTRIAL APPLICABILITY

[0040] As mention d above, by controlling the composition of inclusion included in the alloy material according to the invention to one or more of MnO—SiO2—Al2O3 system, SiO₂ and MgO—Al2O3 is stabilized the inclusion against the etching solution, whereby there can be obtained Fe-36% Ni alloy based material for shadow mask having a good hole shape. Moreover, the invention can be used as a magnetic material or an electric material such as lead frame, bimetal or the like. 

1) A Fe—Ni alloy material for shadow mask having an excellent etching workability characterized by comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.000°-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt % and the reminder being Fe and inevitable impurities, and containing not more than 0.02 wt % of non-metallic inclusion insoluble in an aqueous solution of ferric chloride. 2) A Fe—Ni alloy material for shadow mask having an excellent etching workability characterized by comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.0001-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt %, Nb: 0.01-1.0 wt % and the reminder being Fe and inevitable impurities, and containing not more than 0.02 wt % of non-metallic inclusion insoluble in an aqueous solution of ferric chloride. 3) A Fe—Ni alloy material for shadow mask having an excellent etching workability characterized by comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.0001-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt %, Co: 1-8 wt % and the reminder being Fe and inevitable impurities, and containing not more than 0.02 wt % of non-metallic inclusion insoluble in an aqueous solution of ferric chloride. 4) A Fe—Ni alloy material for shadow mask having an excellent etching workability characterized by comprising Ni: 26-37 wt %, Si: 0.001-0.2 wt %, Mn: 0.01-0.6 wt %, Al: 0.0001-0.003 wt %, Mg: not more than 0.001 wt %, Ca: not more than 0.001 wt %, Nb: 0.01-1.0 wt %, Co: 1-8 wt % and the reminder being Fe and inevitable impurities, and containing not more than 0.02 wt % of non-metallic inclusion insoluble in an aqueous solution of ferric chloride. 5) A Fe—Ni alloy material according to any one of claims 1, 2, 3 and 4, wherein th non-metallic inclusion is one or more of MnO—SiO₂—Al₂O₃ bas d inclusion, SiO₂ inclusion and MgO—Al₂O₃ bas d inclusion. 6) A F —Ni alloy material according to any one of claims 1, 2, 3, 4 and 5, wherein the non-metallic inclusion is one or more of MnO—SiO₂—Al₂O₃ based inclusion having a composition of MnO: 25-50 wt %, SiO₂: 40-60 wt % and Al₂O₃: 5-30 wt %, SiO₂ and MgO—Al₂O₃ spinel inclusion having a composition of MgO: 5-45 wt % and Al₂O₃: 55-95 wt %. 7) A Fe—Ni alloy material having an excellent etching workability according to claim 5 or 6, wherein the MnO—SiO₂—Al₂O₃ based inclusion contains not more than 30 wt % in total of CaO and MgO. 